1. Field of the Invention
The present invention relates to an endoscope apparatus, more particularly, a constitution used in medical fields for forming and displaying a spectral image (video) made up of image information of arbitrarily selected wavelength ranges.
2. Description of the Related Art
Recently, in an electronic endoscope apparatus which uses a solid imaging device, spectral imaging combined with a narrow band pass filter on the basis of a spectral reflectance in alimentary canal (gastric mucosa and the like), namely, a narrow band filter built-in an electronic endoscope apparatus (Narrow Band Imaging—NBI) has become the focus of attention. In place of rotational filters of R (red), G (green) and B (blue) by a frame sequential method, this system is provided with band pass filters of three narrow bands (wavelengths), outputs sequentially illumination light via these narrow band pass filters, and conducts processing the same as in the case of red (R), green (G) and blue (B) signals while changing respective weightings to three signals obtained from these illumination lights, thereby forming a spectral image. This spectral image is able to realize micro-structures and the like in gastrointestinal tracts such as the stomach and large intestine, which would otherwise not be realized.
In contrast, unlike the frame sequential method using the above-described narrow band pass filters, as described in Japanese Published Unexamined Patent Application No. 2003-93336, and Yoichi Miyake “Analysis and Evaluation of Digital Color Images,” University of Tokyo Press, 2000, pp. 148-153, it has been proposed that in the simultaneous method in which micro-mosaic color filters are arranged on a solid imaging device, a spectral image is formed by the computing process on the basis of image signals obtained from white light. In this method, the relationship between numeric data of the respective R, G, and B color sensitivity characteristics and numeric data of spectral characteristics of a specific narrow band pass is determined as matrix data (coefficient sets) and computing is made for the matrix data and the R, G and B signals to obtain spectral image signals artificially via the narrow band pass filters. Where a spectral image is formed by such computing, it is not necessary to provide a plurality of filters corresponding to desired wavelength ranges and to provide these change-over arrangements, thereby successfully avoiding increases in the size of a system and reducing cost.
However, in forming a spectral image in the above-described endoscope apparatus, areas of interest to be visualized are in a plurality of types and conditions such as relatively thick blood vessels, capillary vessels, deep-positioned vessels, shallow-positioned vessels, cancerous tissues different in progression, and the relationship between the targets and the wavelength ranges to be selected may vary depending on the individual differences in areas of interest to be observed, therefore, it is difficult to select and establish a wavelength range for obtaining an optimal spectral image in which an expected target is visualized.
On the other hand, a wavelength range where a difference between specific substances is visualized as a target, for example, a difference between oxyhemoglobin and deoxyhemoglobin, has been clarified, and it is preferable that a spectral image set at a predetermined wavelength range can promptly be obtained.
Further, since the most appropriate wavelength ranges in forming and displaying the spectral image easy to be clinically observed are often different among the operators of the apparatus such as clinical doctors, if the wavelength ranges thought to be optimum are previously prepared in accordance with the regions of the objects, each of the clinical doctors cannot utilize them in forming spectral images, and in some cases, he or she needs to perform the operation of selecting the wavelength ranges suited to his or her feeling by the minute. Accordingly, it takes much time for each operator of the apparatus to form and display the spectral image easiest for the operator to observe.
The invention has been reached in view of the problem described above, and has an object of providing an endoscope apparatus with which each of the operators of the apparatus can quickly form and display a spectral image easiest for the operator to observe.